Precision condenser adjuster



June 13, 1939. v. CLARKE PRECISION CONDENSER ADJUSTER Filed July 9, 1937 fig;- 25 iL w-q 62 I w a. 46 l 12 5 I I I IIJI INVENTOR &.; ATTORNEYS Patented June 13, 1939 UNITED STATES eATEN'r OFFlCE v PRECISION CONDENSER ADJUSTER Victor Clarke, Coral Gables, Fla.

Application July 9, 1937, Serial Ne. 152,749

5 Claims.

This invention relates to a precision adjusting device for instruments and the like and, by way of example, may be applied to the tuning mechanism of compact radio transmitters and receivers in which the adjusting mechanism is placed within a comparatively small space.

An object of the invention is to produce an adjusting construction of small size which allows extremely accurate micrometric adjustment of a movable element.

One form of device embodying the invention may be utilized in conjunction with an oscillator coil and associated variable condenser in a radio transmitter. The variable condenser may be positioned in the interior of the coil in order to conserve space, and the adjusting mechanism may be located at the top of the coil and associated with the condenser shaft.

The precision adjuster generally consists of a resilient member tending to displace the condenser shaft angularly in one direction; angular displacement being resisted and controlled by means of a micrometrically adjustable member.

In one form of the invention, the condenser shaft may be provided with a lever which is engaged by a coil spring normally urging the lever and the condenser shaft in one direction. The micrometric means may suitably consist of a set-screw which bears against the opposite side of the arm and upon adjustment causes a limited angular movement of the arm and the condenser shaft. If desired, the set-screw may be calibrated so that a known variation in capacity of the condenser may be obtained by rotating the setscrew through one or a fraction of a complete revolution.

This construction has many advantages, such as for example, small and compact size, and the ability to be adjusted with extreme accuracy and to retain the accurate adjustment over long periods of time without the necessity of recalibrating or readjusting.

Other advantages will be apparent from the description of a typical form of adjusting a mechanism embodying the invention, such as that disclosed in the accompanying drawing, in which:

Figure 1 is a top plan View of an oscillator coil enclosing a variable condenser and the condenser adjusting device of the present invention;

Figure 2 is a side View of the oscillator coil, partly broken away to show details of the adjusting mechanism, and

Figure 3 is a view in section taken on line 3-3 of Figure 1.

In the form of the invention illustrated, the adjusting mechanism is disclosed as applied to a variable condenser l0, located in the interior of a coil l2, for use in transmitters or receivers operable on several frequencies. be of any desired type and is illustrated as having a number of turns of wire l4, supported on a cylindric tube It of insulating material and being provided with prongs l8 engageable in a socket receiver.

For convenience in allowing interchangeable use of coils tuned to a definite frequency and to render the coil unit as compact as possible, the variable condenser l0 may be supported on the base of the coil l2 and is connected in a known manner to the coil terminals. Supported in the are retained in engagement with the walls of the tube It by means of bolts or set-screws 24. The cross-bar 20 may be provided with a central aperture 26 through which passes a collar 28 forming a part of the frame of the condenser l9. The bar 2% and condenser It may be locked together by means of nuts 30, threaded on the collar 28 on opposite sides of the bar.

The condenser shaft 32 passes through the collar 28 and is adapted to receive on its outer end a lever 34 provided with a bore 36 and split end 38, the arms of which may be drawn together by a set-screw 40 to grip the condenser shaft 32. The opposite end of the lever 34 is provided with an enlarged disk-like portion 42, which is adapted to bear against a set-screw 44, threaded in one arm 46 of a yoke 48 fixed to the bar 29. The set-screw 44, if desired, may be calibrated and provided with indicia so that each turn or fraction of a turn will produce a predetermined variation in the capacity of the condenser by rotation of the condenser shaft 32. The enlarged arm portion 42 is urged against the set-screw 44 by a coil spring 50 disposed between the portion 42 and another arm 52 on the yoke 48. The arm 52 may be provided with an inwardly directed stud 54 which is received within the spring 50. The enlarged portion 42 of the lever may be provided also with a recess for receiving the opposite end of spring 50, thereby cooperating with the stud 54 to retain the spring in an operative position. To permit adjustment of the condenser, the tube I6 may be provided with apertures 56 and 58 which are in alignment with set-screws 44 and 40 respectively so that The coil 10 may I (not shown) in a radio transmitter or an implement may be inserted for' rotating the set-screws. q

The condenser l may be adjusted to desired capacity by rotating the condenser shaft 32 with the lever loosely supported upon it to approxi- .mately the final adjusted position. The setscrew 40 is then tightened to clamp the lever 34 tightly to the shaft 32.

V screw Gllspanning a split 62 communicating with the threaded aperture in the arm 46.

Where extreme accuracy is required over a Wide temperature range, an error'will be introduced with theuse of the more common metals or, alloys dueto thermal expansion, or contraction, of various partsof the condenser adjuster and. espeoially thslet-srew 44. This error can beminimized by the use of some material having a low coefficient of-temperature expansion such as Invar. Another detail of construction to eliminate the effect of expansion in the lever is e to design the parts sothat the plane of the surface of the-lever, which comes in' contact with th u h th center line of I c the set screw goes m g e V e J'ustably mounted on said shaft and disposed'be 7 tween the ,arms of the yoke, a screw threaded the shaft to be controlled. 7

It will be understood from the above description that I have produced an efiective and extremely accuratemechanism for adjusting the movableblementcf' any form of instrument or the' like.

'It will also be understood that V the construction illustrated may be varied, as desired, without departing from the invention. Therefore, the embodiment disclosed should be considered illustrative only, and not as limiting thescope of the claims.

, Iclaim: V 1

r 1. In an adjusting device, .the combination of asliaft, a lever fixed to said shaft and angularly adjustable with relation thereto, a yoke member, a set-screw threaded into said yoke and having ,a free end engaging said lever, and resilient 'meansjenga'ging the yoke and the lever for urging the lever into engagement with the free end of the set-screw.

2. Inan adjusting device, the combination of a shaft, a lever fixed'to said shaft and angularly adjustable with relation thereto, a yoke member, a set-screw threaded into said yoke and engaging said lever to vary the angular dis- *placement of the shaft and a coil spring bearing against said lever'and said yoke for urging the lever against the set-screw.

V 3. In an adjusting device, the combination of a support, a shaft mounted in said support, a

yoke member having spaced arms mounted on said support, a lever adjustably mounted on said shaft and disposed between the arms of the yoke, means mounted on one of the yoke arms and adjustable relatively thereto engaging the lever to vary the angular displacement of the shaft, means for locking in adjusted position the means to vary the angular displacement of the shaft and resilient means bearing against the lever' and the other yoke arm to urge the lever into engagement with adjustable means.

4. In an adjusting device, the combination of a support; ashaft' mounted in said support, a

yoke member having spaced substantially parallel arms mounted on said support, a lever adarms of the yoke, a' screw threaded through 7 one of the arms and engaging the lever to vary the "angular displacement of the shaft, and a coil spring bearing against the lever and the other yoke arm to urge the lever against the set-screw. f

VICTOR CLARKE. 

